Electrical contact device



p 19, 1950 H. H. RAYMOND 2,522,895

ELECTRICAL CONTACT DEVICE Filed July 24, 1946 awe/Mm HORACE H. RAMON Patented Sept. 19, 1950 UNITED STATES PATENT OFFICE ELEOTRICAL C ZSZ ACT DEVICE Horace H. Raymond, Berlin, Conn, assigner to Raymond Engineering Laboratory, Inc.,-, Berlin, Conn, a corporation of Connecticut Application July 24, 1946, Serial No. 685,944

12 Claims. 1

The invention relates particularly to an electrical contact device adapted for use with or as a part of an indicating instrument. An altimeter may be taken as an example of an instrument with which the contact device may be used and the invention is shown and described in combination with an altimeter, but it will be understood that the invention is equally applicable for use with indicating instruments of other types.

In fact, as to some of its broader aspects the invention is not necessarily limited for use with an indicating instrument.

The mechanism of an instrument such as an altimeter is delicately responsive to atmospheric pressure or to some other value or amount which the instrument is designed to indicate. It is sometimes desirable to utilize such an instrument not only for indicating pressure or some other amount, but also for making an electric connection at one or more positions of the indicating hand or hands. When an electrical contact of conventional form is attached to a hand of the instrument for engagement with a stationary electrical contact on the instrument, the mechanical interference caused by the engagement of the two contacts prevents free movement of the hand and the hand is held in stationary position by the contacts until the mechanism of the instrument builds up sufficient force to disengage the contacts. with the proper indication by the instrument of the pressure or other amount to be indicated, but it also places an unnecessary and sometimes injurious load on the delicate mechanism of the instrument. When one or both of these contacts are made extremely flexible so that the moving contact is allowed to touch and pass the fixed contact without undue mechanical interference, failure to make electrical contact results, unless these contacts are made in accordance with the principles of my invention.

I have proved by experiment, under normal conditions of observation, that two pieces of high- 1y conductive metal may be brought together in physical contact without establishing electrical connection and that the electrical resistance at the point of contact will be on the order of millions of ohms. I have proved under natural conditions of experimentation that this condition of high resistance becomes apparent within two minutes after scraping and cleaning the contacts regardless of the purity and stability of the metals used. I have proved that in order to establish electrical connection after physical contact is made it is necessary to force the contacts to- This not only interferes.

.gether so that a relatively high unit pressure is developed between them.

The general object of the present invention is to provide a contact device which is adapted for use with an indicating instrument and which offers such an infinitesimal mechanical resistance to movement as not to interfere to any appreciable extent with the free movement of the indicating hand and of the mechanism of the instrument.

A further and more specific object of the invention is to provide a contact device having the characteristics described which is so formed and constructed as to provide an assured electrical connection at each engagement of the relatively movable contacts, notwithstanding the presence of insulating films which naturally tend to form on all metallic surfaces.

Various other objects of the invention will be apparent from the drawing and from the specification and claims.

In the drawingI have shown in detail a. preferred embodiment of the invention, but it will be understood that various changes may be made from the construction shown, and that the drawing is not to be construed as defining or limit ing' the scope of the invention, the claims forming a part of this specification being relied upon for that p rpose.

Of the drawing:

Fig. .1 is a front view of an instrument having incorporated therein an electrical. contact device embodying the invention.

Fig. 2 is a side view of the instrument shown in Fig. 1.

Fig. 3 is a fragmentary sectional view taken along the line 3-3 of Fig. 1.

Fig. 4 is an enlarged side view of the instrument hands together with an electrical contact carried by one of them.

Fig. 5 is a front view of one of the hands shown in Fig. 4 together with the electrical contact carried thereby.

Fig. '6 is an enlarged fragmentary perspective view showing the relationship of the two contacts of the contact device when engaged with each other.

In accordance with the invention, two contact carrying members are provided which are provided respectively with electrical contacts adapted to engage each other. Preferably one member carries two or .more relatively rigid contacts spaced apart .in the direction of relative move-: ment .and the other member carries a single resiliently held contact otnovel construction as 4 3 hereinafter fully described. The first said member may advantageousy be stationary and the second said member may advantageously be movable.

I have illustrated an altimeter which is a representative instrument to which the invention is particularly applicable, but it will be understood that the invention is not in any way limited to an altimeter. In Figs. 1 and 2 the altimeter in its entirety is represented at I6, the altimeter having a body [2 containing the mechanism thereof and having a, face or dial l4 with numerals thereon arranged circumferentially. The altimeter has two hands l6 and I8 carried by rotatable pintles l1 and [9 controlled by the mechanism of the instrument and serving in cooperation with the numbers on the dial to indicate altitude corresponding to various atmospheric pressures. Theconstruction and calibration of the instrument are such that the hand l6 indicates the altitude in hundreds of feet and that the hand i8 indicates the altitude in thousands of feet.

Preferably the hand 18 of the instrument is specially constructed to constitute the movable contact member, this member or hand carrying a movable electrical contact 20. The stationary contact member is held by the body of the instrument and is provided with one or more stationary contacts 22, 22 with which the contact 20 is adapted to engage as the hand [8 is moved. I have shown twelvestationary contacts 22, 22 spaced uniformly about the periphery of the dial H, but the invention is not limited to any particular number of contacts nor to any particular angular spacing of these contacts.

As shown in Fig. 3, the body l2 of the instrument is engaged by a ring 24 behind which the dial I4 is located. Adjacent the ring 24 is a ring 26 of insulating material having imbedded therein an annular metallic plate or ring 28, the inner portion of which extends inward. An annular gasket 30 is interposed between the ring 26 and the body l2, and the ring 26 is held in place by a cover 32 which is secured to the body 12 by means of screws 34, 34. The front of the instrument is closed by a glass plate 36 separated from the ring 26 by means ofa gasket 38. A threaded ring 40 engages the cover 32 to hold the glass plate in place.

The metallic ring 28 serves as the support for the stationary electric contacts 22. As shown more clearly in Fig. 6, each stationary contact 22 is formed as a part of a wirewhich is bent to provide two parallel portions which extend respectively through two transverse holes in the plate or ring 28 near the edge thereof. The wire is further bent to provide a third portion parallel with the aforesaid portions and extending past the edge of the plate, transversely of the plate but longitudinally of the instrument. The end part of the last said portion constitutes the actual contact. The wire constituting each contact 22 is preferably soldered to the plate 28 to insure good electrical connection. The contacting portion of each contact 22 is perpendicular to the direction of relative movement between the contacts 20 and 22, 22.

In order to provide an electrical circuit through the contacts 22, 22, the metallic ring 28 is formed with an integral lug 42 which extends outward beyond the ring 26 into a recess formed in the cover 32. A conductor 44 is electrically connected with the lug 42 and extends through an aperture in a flange on the body [2 into a metallie conduit 46 secured to the body [2 by means of a clamping band 48. The conduit 46 carries a cable connector 50 into which the conductor 44 extends. A current limiting resistor 52 is preferably connected in the conductor 44. A second conductor 54 extends through the connector 50 and is grounded to the body of the instrument, being thus electrically connected with the hand l8 and with the movable contact 20. The conductors 44 and 54 are connected with a suitable source of current and with a suitable relay device or other instrument to be actuated upon the completion of the circuit.

The hand [8 serves as a support for the movable contact 20 and this contact is preferably an extremely thin, flat, flexible metallic strip. It was originally proposed to provide a long strip such as 20 so positioned that one fiat side thereof would engage with the stationary contacts 22,

22, and this arrangement was found to be entirely satisfactory as concerns the provision of a minimum mechanical resistance to relative movement. It was found, however, that the flexibility of the strip was so great that the contact pressure with each stationary contact 22 had a very low unit value, the result being that there Was frequent failure to form satisfactory electrical connection by reason of insulating films which would form on the contacts. In fact it was found that the flexible strip, on account of the varying surface conditions thereof, would in some instances establish two or more successive electrical connections as it wiped across a single stationary contact. This succession of electrical connections would cause chattering of the relay or other instrument in the circuit and would thus result in false operations which made the device useless for its intended purpose.

To avoid the difficulties above described, the strip which comprises the contact 20 is so arranged that at least the portion 20 thereof that engages the contacts 22, 22, is positioned in a plane paralel or substantially parallel to the direction of movement so as to be engageable at one of its edges with the contacts 22, 22 instead of at one of its fiat faces. Furthermore, the contacts 22, 22 are preferably formed with knife edges, the result being that the extremely narrow strip engaging edgewise with a knife edge gives a very high unit contact pressure, this being true even though the strip is resiliently and yieldably mounted on its support to provide a minimum of mechanical resistance to relative movement.

The resilient and yieldable mounting of the edgewise positioned portion 20 of the strip may be variously effected, but preferably and as shown, a long strip 56 is provided of which the contact 20 constitutes the outer portion. The strip 56 is bent or twisted through a angle to provide a flexing portion 58 which is perpendicu lar or substantially perpendicular to the direction of movement and to also provide the aforesaid edgewise engaging portion or contact 20 which is parallel or substantially parallel to the said direction. The flexing portion 58 of the strip constitutes a resilient mounting for the engaging or contact portion 20 thereof. The said flexing and engaging portions of the strip are substantially straight and substantially in alignment.

When used in conjunction with a sensitive instrument such as an altimeter, the metallic strip 56 is very small so as to offer a minimum of resistance to the movement of the hand [8. The strip 56 may advantageously be a gold ribbon having a thickness: onthe order of .001 and having a width on the order of .01". The size of the strip 56 is greatly exaggerated in the drawing.

For supporting the strip 56 on th support or hand I8 there is provided a relatively rigid element fixedly connected with the said hand and extending therefrom approximately perpendicular to the direction of relative movement. This element is preferably a stiff wire (iii which extends through the head of a-button 62, the button being provided with a shank which extends through an aperture in the hand it and is riveted over at the inner side thereof- The inner end olth'e wire 68 is bent transversely, as shownat 64, and the end of the flexing portion53 of the strip 56 issoldered to the said portion 64. The portion 58 of. the strip is loaded or biased so as to be normally in contact with the outer end portion of the wire 60-, the wire thus serving; to preclude the possibility of uncontroiled. vibration of the strip with resultant variations in th re.- lationship between the contact portion. 25 thereof and'the several contacts 22,22. By means of the wire. the strip is normally held in fixed relation with the supportior hand l8.. Preferably the wire 60 is formed at its outer end. with a loop 66 through which the portion-58' of thestrip extends, and the said strip portion bears against one side of the loop, preferably the. side which is at the rear with respect to the direction: of motion. In additionto the loop 66', the wire is preferably also provided with a loop 68. between its ends andthestripportion 58 normally extends through this loop without en agement therewith. The function ofthe loop 62 is. to retain. the strip 56 inapproximately its normal position in the event of severe shock or vibration; The strip is so extremely light and flexible that severe shock. or vibration would deflect it and possibly withdraw it from the loop 66. The hand [8 is provided with a weight it) to counterbalance the weight 'of the strip 56, of the wire 602 and the button 62;

While I have shown and described the edgewi'se engaging portion 20 constituting. the m'ovable contact as being formed as an integral portion of a long strip. 5B, it will be understood that the invention in its broader aspects is not necessarily so limited and that the said engaging portion may be otherwise resiliently and yieldably mounted on its-support. As concerns the broader phases of the invention, it is merely essential that the: engaging portion. 2i). be formed of extremely thin metal and that it be resiliently and yieldably supported so as to have edgewise engagement withthe other contact which preferably has a knife edge, and that it be positioned accurately by pro-loading or otherwise so as to be". normally in fixed relationship to its support. It. was reasonably suggested that the edge to edge engagement of th contacts 22, 22 and 20 would cause excessive wear or. burning thereof, particularly on accountof the extreme thinness of: the contact 2i However, exhaustive tests have. been made and in one such test an altimeter having. contacts embodying the invention was operated over 5,090 times and the engaging port'ioni2ll. of the strip '56. was then subjected to microscopic examination. This examination failed'to. disclosev any indication of weanburning Or pitting; It willbe observed that the knife edges of the contacts 22, 22' are shown as facing inthecloc'ks wisea direction; The hand I8 and the: contact 20 move. in. the counterclockwise direction for noriii) mal engagementwith the contacts 22-, 22 as shown in Fig. 6. As eachcontact 22 is engaged an electrical circuit is established through the con ductors 44 and 54; Continued movement of the hand l8' causes the contact 20- to slip over and disengage itself from each contact 22, the contact 20 being then ready for engagement with the next contact 22. The contact 20 disengagesitself from each contact 22 with a snap action, thus effecting a quick break and minimizing arcing. At the instant of engagement the contact 20' preferably overlaps each contact 22 by only a few thousandths of an inch and the duration of engagement may be very short. When the hand I8 is returned'in the clockwise direction the contacts will incidentally engage, but such engage.- ment is not. utilized. for completing the circuit.

When the contacts 22, 22 are. arranged in a series for successive engagement by the contact 20, the. knife edges of the said contacts all face in thesame direction; However, the inventionis not necessarily so limited as it may in some instances be desirable for the contact 20 to merely oscillate between two contacts 22, 22. In this latter case the knife edges would face in opposite directions instead of in the same direction.

The contacts 22, 22 are preferably adjustable in the direction of their spacing and in the di-- rection of the relative movement, in order that the spacing between them may be accurately determined. A special adjusting means may be provided for each contact, but for the sake of simplicity I take advantage of the peculiar mounting. and construction of the said contacts that has already. been described. Each contact comprises a portion which extends transversely of the direction of spacing and of the direction of relative movement. Adjustment of. the'zspac ing may be conveniently effected by slightly bending the several projecting portions of the contactsin one direction or the other as required.

What I claim is 1 The combination in .an electrical contact device of a stationary contact support, a second contact support movable about a fixed pivotal axisv and in a path adjacentthe stationary contact support, a stationary electrical contact on the stationary contact support having a knife edge parallel with the said pivotal axis and facing. in a direction. perpendicular to a radius through the said an extremely thin flat strip of metal carried by the movable support and. having at least a portion thereof which is ina plane perpendicular to the said pivotal axis and which constitutes an electric contact engageable at one edg with the knife'edge of the said stationary contact, and means for resiliently and yieldably connecting the said strip portion withithe said movable support for relative movement'in the said. perpendicular plane.

2. The combination in an electrical contact device,v of two relatively movable contact members provided respectively with electrical contacts, one

' of the. members including a support and a flat flexible strip of metal which engages at one .end with the support and is twisted between its ends to provide a flexing portion adjacent the support and located in a plane substantially perpendicular to the direction of relative movement and to provide an engaging portion at its free end located in-a plane substantially parallel to the said direction,'the said engaging portionof the strip constituting: the electrical contact of the last said member and being engageable: at one: edge. with the electrical contact of the other member to establish an electrical connection.

3. The combination in an electrical contact device, of two relatively movable contact members provided respectively with electrical contacts, one of the contact members having its contact formed with a knife edge substantially perpendicular to the direction of relative movement and the other of the contact members including a support and an extremely thin flat flexible strip of metal which engages at one end with the support and is twisted between its ends to provide a flexing portion adjacent the support and located in a plane substantially perpendicular to the direction of relative movement and to provide an engaging portion at its free end located in a plane substantially parallel to the said direction and substantially perpendicular to the aforesaid knife edge, the said engaging portion of the strip constituting the electrical contact of the second said member and being engageable at one edge with the knife edge of the contact of the first said member to establish an electrical connection.

4. The combination in an electrical contact device, of two relatively movable contact members provided respectively with electrical contacts, one of the members having its contact formed with a knife edge substantially perpendicular to the direction of relative movement and the other of the contact members including a support and a narrow flat flexible strip of metal engaging at one end with the support and having a thickness on the order of .001 and twisted between its ends to provide a flexing portion adjacent the support and located in a plane substantially perpendicular to the direction of relative movement and to provide an engaging portion at its free end located in a plane substantially parallel to the said direction and substantially perpendicular to the aforesaid knife edge, the said engaging portion of the strip constituting the electrical contact of the last said member and being engageable at one edge with the knife edge of the contact of the first said member to establish an electrical connection.

5. The combination in an electrical contact del vice, of two relatively movable contact members provided respectively with electrical contacts, one of the members having its contact formed with a knife edge substantially perpendicular to the direction of relative movement and the other of the contact members including a support and a narrow fiat flexible strip of metal engaging at one end with the support and having a thickness of .001" and having a width on the order of .01" and twisted between its ends to provide a flexing portion which is in a plane substantially perpendicular to the direction of relative movement and to provide an engaging portion at its free end located in a plane substantially parallel to the said direction and substantially perpendicular to the aforesaid knife edge, the said engaging portion of the strip constituting the electrical contact of the last said member and being engageable at one edge with the knife edge of the contact of the first said member to establish an electrical connection.

6. The combination in an electrical contact device, of two relatively movable contact members provided respectively with electrical contacts, one of the contact members having its contact formed with a knife edge substantially perpendicular to the direction of relative movement and the other of the contact members including a support and an extremely thin flat flexible strip of metal which engages at one end with the support and is twisted between its ends to provide a flexing portion held by the support and located in a plane substantially perpendicular to the direction of relative movement and to provide an engaging portion at its free end located in a plane substantially parallel to the said direction and substantially perpendicular to the aforesaid knife edge, the said engaging portion of the strip constituting the electrical contact of the second said member and being engageable at one edge with the knife edge of the contact of the first said member to establish an electrical connection, and means for moving one contact member relatively to the other along a fixed path so positioned that the engaging portion of the strip constituting the contact of one member with the knife edge of the contact of the other contact member to establish an electrical connection and then disengages the said contact of the other member with a snap action to break the electrical connection.

'7. In an electrical contact device, the combination of two contact members provided respectively with electrical contacts, one of the members being movable relatively to the other to effect engagement and disengagement of the contacts and one of the contact members comprising a support, a relatively rigid element fixedly connected with the support and extending therefrom substantially perpendicularly to the direction of relative movement, a thin flat flexible strip of metal havin a flexing portion in a plane substantially perpendicular to the direction of relative movement and adjacent and substantially parallel to the rigid element and also having an engaging portion at the outer end thereof in a plane substantially parallel to the said direction of relative movement which last said portion constitutes the electrical contact of the last said member and is engageable at one edge with the contact of the other member, and means for rigidly attaching the said flexing portion of the strip at its inner end to the support and for biasing the said flexing portion that it normally engages with and is supported by the rigid element near the juncture of the said flexing portion with the said contact portion.

8. In an electrical contact device, the combination or" two contact members provided respectively with electrical contacts, one of the members being movable relatively to the other to effect engagement and disengagement of the contacts and one of the contact members comprising a support, a. relatively rigid element fixedly connected with the support and extending therefrom substantially perpendicularly to the direction of relative movement, a transverse loop on the rigid element near the outer end thereof, a thin flat flexible strip of metal having a flexing portion extending through the loop which flexible portion is located in a plane substantially perpendicular to the direction of relative movement and is adjacent and substantially parallel to the rigid element, the said flat flexible strip of metal also having an engaging portion at the outer end thereof beyond the loop and in a plane substantially parallel to the said direction of relative movement which last said portion constitutes the electrical contact of the last said contact member and is engageable at one edge with the contact of the other contact member, and means for rigidly attaching the said flexing portion of the strip at its inner end to the support and for biasing the said flexing portion so that it normally engages and is supported by one side of the loop on the rigid element.

9. In an electrical contact device, the combination of two contact members provided respectively with electrical contacts, one of the members being movable relatively to the other to effect engagement and disengagement of the contacts and one of the contact members comprising a support, a relatively rigid element fixedly connected with the support and extending therefrom substantially perpendicularly to the direction of relative movement, a transverse loop on the rigid element near the outer end thereof, and a thin flat flexible strip of metal having a flexing portion extending through the loop and located in a plane perpendicular to the direction of relative movement and adjacent and substantially parallel to the rigid element and also having an engaging portion at the outer end thereof in a plane substantially parallel to the said direction of relative movement which last said portion constitutes the electrical contact of the said member and is engageable at one edge with the contact of the other member, the said flexing portion being rigidly attached at its inner end to the support and being positioned for engagement with one side of the said loop on the rigid element, and a second transverse loop on the rigid element between the ends thereof through which the flexing portion of the strip normally extends without engagement, the said second loop serving to hold the strip in approximately its normal position in the event of severe vibration.

10. The combination in an electrical contact device, of a flat metal plate having two spaced holes therein near one edge thereof, a wire bent to provide two parallel portions extending respectively through the said holes, the said wire being further bent to provide a third portion parallel with the aforesaid portions and extending transversely past the said edge of the plate to constitute a stationary electrical contact, and a contact member movable in a direction generally parallel with the said edge of the plate, the said movable contact member including a resiliently mounted contact which is engageable with the stationary contact.

11. The combination of an indicating instrument having a pintle rotatable by the mechanism thereof, a stationary electrical contact, a hand carried by and rotatable with the pintle, and a contact carried by the hand and comprising a narrow and extremely thin flat flexible strip of metal having a flexing portion in a substantially radial plane and having an engaging portion carried by the flexing portion and located in a plane perpendicular to the axis of the pintle and positioned for edge engagement with the stationary contact when the hand is rotated.

12. The combination of an indicating instrument having a pintle rotatable by the mechanism thereof, a stationary electrical contact having a knife edge, a hand carried by and rotatable with the pintle, and a contact carried by the hand and comprising a narrow and extremely thin flat flexible strip of metal having a flexing portion in a substantially radial plane and having an engaging portion carried by the flexing portion and located in a plane perpendicular to the axis of the pintle and positioned for edge engagement with the knife edge of the stationary contact when the arm is rotated,

HORACE I-I. RAYMOND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 807,568 Mitchell Dec. 19, 1905 1,198,340 Garretson Sept. 12, 1916 1,214,771 Fortier Feb. 6, 1917 1,412,451 Collins Apr. 11, 1922 2,180,921 Churchill Nov. 21, 1939 2,309,040 Boemle Jan. 19, 1943 

